Chex 0.1.91

What's Changed

• Migrate references to jax.lib.xla_extension to jax.extend. by @copybara-service[bot] in #403
• Add assert_tree_shape, which is like assert_shape, but for all leaves in a tree. by @copybara-service[bot] in #404
• Use format_shape_matcher when constructing the assert_tree_shape error message. by @copybara-service[bot] in #405
• Migrate to pyproject.toml by @copybara-service[bot] in #406
• release v0.1.91 by @copybara-service[bot] in #407

Full Changelog: v0.1.90...v0.1.91